A CMP (Chemical Mechanical Polishing) method is used to flatten a material layer on a semiconductor substrate. In the CMP method, the material layer on the semiconductor substrate is polished with an abrasive while slurry is supplied onto the abrasive.
However, if abrasive particles of the slurry remain on the semiconductor substrate after polishing the material layer by the CMP, deposits (such as a silicon dioxide film, a silicon nitride film, and amorphous silicon) are likely to adhere onto or around the abrasive particles at the subsequent steps. If the deposits peel off the semiconductor substrate at the following steps, the peeled deposits cause particles, which lead to a decrease in the yield.
Furthermore, generally, the abrasive particles of the slurry are positively charged. On the other hand, many of material layers such as silicon and a silicon dioxide film are negatively charged. The abrasive particles are thus likely to adhere to the material layer. The abrasive particles having adhered to the semiconductor substrate are conventionally removed by scrub cleaning with PVA (Polyvinyl Acetate) after the CMP. However, even after the scrub cleaning, the abrasive particles are likely to remain at end portions of the semiconductor substrate (exposed portions of the semiconductor substrate). Furthermore, when the semiconductor substrate is dried after the scrub cleaning, the abrasive particles remaining on the semiconductor substrate are firmly fixed to the semiconductor substrate and become harder to be removed. Therefore, even when the scrub cleaning is performed, the problem of the particles caused by the deposits still occurs.